Method and device for carbonification of crop straws

ABSTRACT

The present invention is to provide a method for carbonification of crop straws and a device thereof. Pyrolysis process is controlled by regulating the feeding of oxygen during said pyrolysis process, and pyrolysis and carbonification are respectively conducted in separate pyrolysis and carbonification pools, wherein the straws are pyrolyzed in said pyrolysis pool and entered into said carbonification pool to be carbonified. The present invention can quickly raise the temperature of the pyrolysis process, shorten the time of the pyrolysis process, and improve the pyrolysis carbonification efficiency.

FIELD OF INVENTION

This invention relates to a field of pyrolysis carbonificationtechnology for straws, and in particular, a method and a device forcarbonification of crop straws.

BACKGROUND OF THE ARTS

Carbonification of crop straws plays an important role in the generalutilization of straws. Methods and Devices for carbonification of cropstraws become much well developed during the technology development, butsome drawbacks still exist.

For example, as described in the Chinese Patent ZL200510044136.3 titledwith “carbonification process for vegetation with high temperature andfloating oxygen”, which requires two furnace bodies, i.e. inner furnacebody and outer furnace body, wherein the entrance of the furnace chamberis open, and when the carbonification process begins, the vegetation isfed to the inner furnace through the entrance of the furnace chamber andfired to rapidly decompose, with combustible gases of high temperatureexhausted to rise and fully contact with the floating oxygen in the airto form flames, and then the entrance of the furnace chamber is closed,and the vegetation continues to feed to keep the carbonification processin force, until the carbonification process is finished and thus thetemperature is quickly lowered to below the firing point. However, theabove vegetation carbonification process has following disadvantages.Because the flame of vegetation thrown into the inner furnace seals theentrance of the furnace chamber of the inner furnace and thus the aircannot enter the lower portion of the inner furnace, the vegetationsubsequently fed cannot be easily and completely carbonified. After thecarbonification process is finished, it is complicated to discharge thecharcoal from the inner furnace, and auxiliary time for discharging,etc. is longer in comparison with the time for pyrolysiscarbonification. And the labor intensity of workers is heavy, anddischarge cannot be performed until all the vegetation thrown into theinner furnace is carbonified and the temperature is reduced for a longtime. After a previous discharge, operations to fill, carbonify anddischarge is once again taken, resulting in time consuming and lowerproduction rate. Furthermore, since the equipment takes a form ofstationary structure, the cost for transporting crop straws is extremelyhigh, and thus requirements of high efficiency, low cost and productionin large scale cannot be fulfilled.

It is described in the Chinese Patent ZL01132888.6, titled with “Adevice for carbonification of by-products of crop straws, etc.”, thedevice comprises a bottom opening provided in the bottom of acylindrical container with a top cover, and a heat flux tube passingvertically through the bottom opening. An upper end of the heat fluxtube terminates at a distance of 10 cm to the top of the cylindricalcontainer, and the lower end thereof projects 3 cm downwards from thebottom of the cylindrical container to form a horizontal opening at theside of the cylindrical container. A gas tube communicating withhorizontal opening is provided on the cylindrical container and projectsoutwardly. A skirt-shaped base is provided at the lower end to supportthe whole cylindrical container, with a portion thereof opened ascombustion opening. Heat insulation layers are provided at the sides andthe top of the cylindrical container, and on the cover. After the fireis distinguished, carbonification products carbonified by thecarbonification device is stored for 24 hours and then taken out afterremoving the cover. Thereafter, a next carbonification process isstarted. These limit the production rate of the carbonification of cropstraws. Since the carbonification device takes a form of stationarystructure, the cost for transporting by-products of crop straws isextremely high, and the requirements of high efficiency, low cost andproduction in large scale cannot be fulfilled.

If a traditional kiln is used to carbonify crop straws, the productionrate is high. However, the production cycle is quite long from severaldays up to tens of days, the efficiency and the safety are low, and theeconomical profit is not good. Solutions to problems of discharging thefloating particles and poor environmental performance caused by thecollection of wood tar and straw vinegar solution cannot be found, andthus it is not worth promoting.

SUMMARY OF INVENTION

An object of this invention is to solve the problems in prior art, suchas low efficiency in pyrolysis carbonification, high cost forcarbonification of crop straws and limited production scale. The presentinvention is to provide a method and a device for carbonification ofcrop straws so as to satisfy the requirements for pyrolysiscarbonification of different crop straws.

In order to achieve the above object, the present invention provides amethod of producing charcoal from crop straws, comprising a pyrolysisprocess and a carbonification process, wherein said pyrolysis process iscontrolled by regulating the feeding of oxygen during said pyrolysisprocess, and the pyrolysis process and the carbonification process arerespectively conducted in separate pyrolysis and carbonification pools,in which pyrolysis pool the straws are pyrolyzed and entered into saidcarbonification pool to be carbonified.

In the method of producing charcoal from crop straws according to thepresent invention, the pyrolysis process and the carbonification processare separated by performing the pyrolysis and the carbonificationprocesses in different units of the device, so that the productionefficiency is improved. At the same time, the temperature of the cropstraws in the pyrolysis pool is quickly raised by a controllable oxygenfeeding method during the pyrolysis process, and then the crop strawsare dried, preheated and quickly pyrolyzed.

In order to achieve the above object, the present invention furtherprovides a combined device for carbonification of crop straws,comprising a pyrolysis pool, a carbonification pool and a controllableoxygen feeding pipe, wherein a regulating butterfly valve for the oxygenfeeding pipe is provided at an oxygen feeding port of said controllableoxygen feeding pipe, and a branch oxygen supply port connected to saidcontrollable oxygen feeding pipe is in communication with said pyrolysispool. Said pyrolysis pool and said carbonification pool are two separateunits of the device, wherein one or more furnace grates of turn platetype are provided within said pyrolysis pool, and said carbonificationpool is arranged below a material discharging port of said pyrolysispool and provided with a cover having a one-way ventilator.

The device of the present invention accomplishes the pyrolysis processand the carbonification process in the separate units, so that thepyrolysis carbonification efficiency is raised. In use, the crop strawsare fed into the pyrolysis pool and fired due to the combustibilitythereof, and the crop straws are dried, preheated and are in partpyrolyzed with the heat obtained from the combustion of crop straws.During the procedure, depending on the moisture content of the cropstraws and types of the crop straws, the opening of the oxygen feedingpipe is controlled so as to quickly raise the temperature of the cropstraws, effectively dry and preheat the crop straws, and a part of thepyrolysis degree is controlled so as to make sure the crop straws wouldnot be over-pyrolyzed into ashes; then the furnace gratings are turnedso as to drop the crop straws into the lower portion of the pyrolysispool, and the crop straws are further pyrolyzed without oxygen below thebranch oxygen feeding port. Combustible gases such as CO, H₂, C_(n)H_(m)produced during the pyrolysis carbonification process enter into a spaceover the branch oxygen feeding port of the pyrolysis pool for secondarycombustion so as to raise the temperature of the pyrolysis pool. Afterthe pyrolysis process of the crop straws in the pyrolysis pool isfinished, the crop straws are fed through a material discharging portinto the carbonification pool, and the carbonification pool then isclosed via the cover with a one-way ventilator in a gas tight manner toinsulate oxygen. The carbonification time in the carbonification pool isdetermined, depending on the different applications of the crop strawscarbon.

The present invention further comprises a gas collecting shell providedabove said pyrolysis pool, wherein said gas collecting shell is incommunication with a settlement room through a gas channel, and onestage or several stages of spacers are provided in said settlement room.A top end of said settlement room is in communication with said gaschannel and is provided with a gas discharging port, and an oil-liquidcollector is connected to the lower end of said gas discharging port,with an oil-liquid collecting container below said oil-liquid collector.

The spacer is connected to the wall of the settlement room at one endonly. The upper end of a first stage of the spacer is connected to thetop of the settlement room, and the second stage of the spacer isconnected to the bottom of the settlement room, and so on. Gases fromthe pyrolysis carbonification process enter into one end of thesettlement room through the gas collecting shell and the gas channel,then into another end from below the spacer, and finally discharged fromthe gas discharging port at the top of the settlement room. Through thispath, the travel of the gases is increased with the speed and thetemperature thereof reduced. Floating particles in the gases fall intothe bottom of the settlement room. The oil liquid collector is providedbelow a gas discharging port at the end of the settlement room, viawhich the gases will be discharged into the air. After the gasesentering into the settlement room naturally condense, wood tar and strawvinegar solution contained in the gases are adsorbed by the oil liquidcollector.

In comparison with the prior art, the present invention has followingfeatures: (1) during the pyrolysis process, according to the differencein moisture content of the crop straws and the types of the crop straws,the oxygen feeding is controlled so that the crop straws are higheffectively dried, preheated and pyrolyzed; (2) the pyrolysis processand the carbonification process are separated and accomplished indifferent units, so that the pyrolysis carbonification efficiency isgreatly improved; (3) the combined structure design allows the pyrolysiscarbonification device to be easily transported to the straw productionplace and quickly assembled. A problem of the general crop strawspyrolysis carbonification device being too large to transport or move issolved; (4) It is easily disassembled for transferring. According to thedistribution of the crop straws, the crop straws pyrolysiscarbonification device is timely disassembled to transport to a suitableoperation region so as to reduce the high cost of crop strawstransportation. At the carbonifying site of crop straws, the units arequickly assembled through a base plate, a frame and fasteners. When thecarbonification in an operation region is finished, the device isdisassembled for transporting to another operation region, and then suchdevice is reassembled at that place for carbonification; (5) A gassettlement room is used in the crop straws pyrolysis process. Thefloating particles in the gas flow fall to the bottom of the settlementroom through means in the settlement room. Wood tar and straw vinegarsolution naturally condenses to adhere to the oil liquid collector andflows to the oil liquid collecting container, with the exhausted gasdischarged harmlessly into the atmosphere. It is assured that theproduction procedure is harmless to the environment.

The crop straws charcoal produced by the present invention has variousapplications, e.g. for processing solid fuels utilized by ruralresidences to replace the fossil fuel; for modifying the soil byincreasing the moisture content, the air permeability and the content oforganic materials, so that the crop production is raised and diseasesdue to pests are decreased; for pre-processing the crop straws as rawmaterials of the methane production, resulting in the reduction of thevolume of the crop straws and easy transportation and storage, and thusmore economical and safe production of methane.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustratively shows the structure of this invention;

FIG. 2 illustratively shows the structure of the pyrolysis pool;

FIG. 3 is a top view of FIG. 2.

The reference numbers in the figures represent respectively: 1—pyrolysispool, 2—carbonification pool, 3—oxygen feeding pipe, 4—oxygen feedingport, 5—butterfly valve, 6—branch oxygen feeding port, 7—furnace grates,8—discharging port of the pyrolysis pool, 9—gas collecting shell, 10—gaschannel, 11—settlement room, 12—spacers, 13—gas discharging port,14—oil-liquid collector, 15—oil-liquid collecting container, 16—hollowshaft, 17—hollow shaft branch oxygen feeding ports, 18—ignition device,19—support frame, 20—liftable support plate and 21—rail.

EMBODIMENTS OF INVENTION Detailed Description

This invention is further described with reference to the Figures. Thepresent invention provides a combined crop straw carbonification method,in which a pyrolysis process is controlled by regulating the feeding ofoxygen during the pyrolysis process, and pyrolysis and carbonificationare respectively conducted in separate pyrolysis pool 1 andcarbonification pool 2, wherein the straws are pyrolyzed in the saidpyrolysis pool 1 and the pyrolyzed straws are discharged into the saidcarbonification pool 2 for carbonification.

Corresponding to the above method, the present invention provides a cropstraw carbonification device, comprising a pyrolysis pool 1, acarbonification pool 2 and a regulated oxygen feeding pipe 3, wherein abutterfly valve 5 for the oxygen feeding pipe is provided at an oxygenfeeding port 4 of said regulated oxygen feeding pipe 3, and branchoxygen supply ports 6 connected to the regulated oxygen feeding pipe 3are in communication with the pyrolysis pool 1. The pyrolysis pool 1 andthe carbonification pool 2 are two separate units of the device, whereinone or more furnace grates 7 of turn plate type are provided within thepyrolysis pool 1, and the carbonification pool 2 is provided below adischarging port 8 of the pyrolysis pool 1 and provided with a coverhaving a one-way ventilator.

The pyrolysis pool 1 is mounted on a support frame 19, and thecarbonification pool 2 is located on a liftable support plate 20 whichis below the pyrolysis pool 1 and is placed on a rail 21. Furnace grates7 are fixed to the wall of the pyrolysis pool 1 through a shaft, and thebutterfly valve 5 controls the opening and closing of the oxygen feedingport 4. The regulated oxygen feeding pipe 3 is arranged below thefurnace grates 7 of the pyrolysis pool 1 along the outer wall of thepyrolysis pool 1 and is in communication with the outer wall of thepyrolysis pool 1. The cover (on the carbonification pool 2) with aone-way ventilator is lifted to release gases when the pressure becomeshigh. It is possible that one pyrolysis pool 1 corresponds to one ormore carbonification pools 2. The carbonification pool 2 not only has acarbonification function, but also can be used for a specialcarbonification product, assuring that the pyrolysis process iscontinuous. The branch oxygen supply ports 6 are distributed along theregulated oxygen feeding pipe 3 and are in communication with the insideof the pyrolysis pool 1. The hot gas rises due to the combustion ofstraws in the pyrolysis pool 1, and a pressure difference is presentbetween the external portion and the internal portion of the pyrolysispool 1. Now, if the butterfly valve 5 communicating with the externalportion of the pyrolysis pool 1 is activated, the air outside thepyrolysis pool 1 will, due to the negative pressure, enter into thepyrolysis pool 1 via the regulated oxygen feeding pipe 3 so as to assistthe combustion. During the initial firing period after the straws areentered into the pyrolysis pool 1, the oxygen feeding port 4 is fullyopened so as to rapidly raise the temperature in the pyrolysis pool 1,and therefore, the straws are rapidly dried and preheated. When thetemperature reaches 200-850° C., the opening of the oxygen feeding port4 is gradually decreased to reduce the oxygen into the pyrolysis pool 1,so that it is avoided the straws are over-pyrolyzed into ashes due tothe overfeed of oxygen.

The present invention further comprises a gas collecting shell 9 whichis located above the pyrolysis pool 1 by a support frame 19, wherein thegas collector 9 is in communication with a settlement room 11 through agas channel 10, and a stage or several stages of spacers 12 are providedin the settlement room 11. A top end of said settlement room 11 is incommunication with the gas channel 10 and is provided with a gasdischarging port 13. An oil-liquid collector 14 is connected to thelower end of the gas discharging port 13, with an oil-liquid collectingcontainer 15 below the oil-liquid collector 14. The oil-liquidcollecting container 15 has a shape of cone and through holesdistributed along its surface. The spacer 12 is connected to the wall ofthe settlement room 11 at one end and is spaced apart from the wall ofthe settlement room 11 at another end. For example, the upper end of afirst stage of the spacer is connected to the top of the settlement room11, and the second stage of the spacer is connected to the bottom of thesettlement room, and so on, wherein a gas channel is formed in thesettlement room 11.

The branch oxygen supply ports 6 are arranged to correspond to one ormore of the furnace grates 7 of turn plate type, and the furnace grates7 are controlled in steps. The position of the branch oxygen supplyports 6 is below or aligned with the plane in which the correspondingfurnace grates 7 is located, so that straws on each step of the furnacegrates 7 fully obtain oxygen.

In order to further improve the effect of oxygen utilization on thebasis of the existing structure, the furnace grates 7 of turn plate typeare fixed to a hollow shaft 16 which is in communication with the oxygenfeeding pipe 3 and on which branch oxygen feeding ports 17 are provided,so that the hollow shaft on the furnace grates become an oxygen feedingportion.

An ignition device 18 is provided below the furnace grates 7 of turnplate type and has a structure of platform or plate fixed to the wall ofthe pyrolysis pool 1. During the pyrolysis process, a few of the firedstraws will fall onto the ignition device 18, so that the strawsconsequently fed into the pyrolysis pool 1 will be rapidly ignited.

The present invention comprises primary components, such as thepyrolysis pool 1, the carbonification pool 2, the gas collecting shell9, the settlement room 11, and secondary components. In use, the dry andcombustible crop straws are fed into the furnace grates 7 of thepyrolysis pool 1 and are fired. When the hot gas rises due to thecombustion of crop straws, a negative pressure is created, and enoughoxygen is automatically fed through the oxygen feeding pipe 3 into thepyrolysis pool 1, so that the temperature in the pyrolysis pool 1 israpidly raised, and thus the crop straws are quickly dried andpre-heated, with a portion of the crop straws pyrolyzed. During theinitial pyrolysis period of the crop straws using their own heat,according to the types of the crop straws and their moisture content,the opening of the butterfly valve 5 at the oxygen feeding port 4 isadjusted accordingly. When it is assured that the temperature can bequickly raised by high effectively utilizing heat of the crop straws,overfeed of the oxygen shall be avoided so as to prevent the crop strawsfrom being over-pyrolyzed into ashes. After the crop straws are quicklydried and pre-heated in the pyrolysis pool 1 with a portion thereofpyrolyzed, the furnace grates 7 are turned, and thus all the crop strawson the furnace grates 7 fall into the lower portion of the pyrolysispool 1. During this procedure, a few of the ignited crop straws fallinto the ignition device 18, so that the crop straws subsequently fedinto the pyrolysis pool 1 will be rapidly fired. Most of the crop strawsfallen into the lower portion of the pyrolysis pool 1 continue to, undera state of high temperature and oxygen insulation, rise to a pyrolysistemperature. This process avoids some fiber components of the cropstraws will be combusted to ashes in the state of high temperature dueto overfeed of oxygen. During the severe pyrolysis carbonificationprocess, the primary components of the crop straws such as all thecelluloses, hemicellulose and part of lignin are pyrolyzed andcarbonified. After a temperature rise in the pyrolysis process, the cropstraws enter into the carbonification pool 2 through the dischargingport 8 of the pyrolysis pool, and immediately the cover having one-wayventilator is closed so as to hermetically insulate the carbonificationpool 2 from oxygen, and the carbonification is continued under the cropstraws' heat. The carbonification time of the carbonification pool 2 isdetermined depending on the final application of the crop straws carbon.The gas produced in the pyrolysis process enters into the settlementroom 11 through the gas collecting shell 9 and the gas channel. Thespacer 12 is longitudinally in a direction of gas flow arranged in thesettlement room 1 to separate the settlement room 1, so that the speedof the gas is effectively decreased, and the gas temperature is reduced,resulting in the floating particles fallen to the bottom of thesettlement room 1 and collectively treated. Wood tar and straw vinegarsolution present in the gas during the pyrolysis carbonification processof crop straws will naturally condense to adhere to the oil liquidcollector 14, flow to the oil liquid container 15, and is centrallycollected to be treated, wherein the exhaust gas is harmlesslydischarged to the atmosphere through the gas discharging port 13.

1. A method for producing charcoal from crop straws, comprising apyrolysis process and a carbonification process, characterized in thatsaid pyrolysis process is controlled by regulating the feeding of oxygenduring said pyrolysis process, and pyrolysis and carbonification arerespectively conducted in separate pyrolysis pool (1) andcarbonification pool (2), wherein the straws are pyrolyzed in saidpyrolysis pool (1) and entered into said carbonification pool (2) to becarbonified.
 2. A device for carbonification of crop straws forpracticing the method of claim 1, characterized in that it comprises apyrolysis pool (1), a carbonification pool (2) and a regulated oxygenfeeding pipe (3), wherein a butterfly valve (5) for the oxygen feedingpipe is provided at an oxygen feeding port (4) of said regulated oxygenfeeding pipe (3), branch oxygen supply ports (6) connected to saidregulated oxygen feeding pipe (3) are in communication with saidpyrolysis pool (1), and said pyrolysis pool (1) and carbonification pool(2) are two separate units of the device, and wherein one or morefurnace grates (7) of turn plate type are provided within said pyrolysispool (1), said furnace grates (7) being connected to a shaft or severalshafts, and wherein said carbonification pool (2) is located below amaterial discharging port (8) of said pyrolysis pool (1) and is providedwith a cover having a one-way ventilator.
 3. A device forcarbonification of crop straws according to claim 2, characterized inthat it further comprises a gas collecting shell (9) provided above saidpyrolysis pool (1), wherein said gas collecting shell (9) is incommunication with a settlement room (11) through a gas channel (10),and a stage or several stages of spacers (12) are provided in saidsettlement room (11), a top end of which settlement room (11) is incommunication with said gas channel (10) and is provided with a gasdischarging port (13), and wherein an oil-liquid collector (14) isconnected to the lower end of said gas discharging port (13), with anoil-liquid collecting container (15) below said oil-liquid collector(14).
 4. A device for carbonification of crop straws according to claim2 or 3, characterized in that said branch oxygen supply ports (6) arearranged to correspond to one or more of said furnace grates (7) of turnplate type, and said furnace grates (7) are controlled in steps, andwherein the position of said branch oxygen supply port (6) is below oraligned with the plane in which said corresponding furnace grates (7) islocated.
 5. A device for carbonification of crop straws according toclaim 2 or 3, characterized in that said furnace grates (7) of turnplate type are fixed to hollow shafts (16) in communication with saidoxygen feeding pipe (3) and provided with branch oxygen feeding ports(17).
 6. A device for carbonification of crop straws according to claim4, characterized in that said furnace grates (7) of turn plate type arefixed to hollow shafts (16) in communication with said oxygen feedingpipe (3) and provided with branch oxygen feeding ports (17).
 7. A devicefor carbonification of crop straws according to claim 2, 3 or 6,characterized in that an ignition device (18) is provided below saidfurnace grates (7) of turn plate type.
 8. A device for carbonificationof crop straws according to claim 5, characterized in that an ignitiondevice (18) is provided below said furnace grates (7) of turn platetype.